U.S. patent number 10,186,787 [Application Number 15/695,910] was granted by the patent office on 2019-01-22 for slot radar antenna with gas-filled waveguide and pcb radiating slots.
This patent grant is currently assigned to Honeywell International Inc.. The grantee listed for this patent is Honeywell International Inc.. Invention is credited to David C. Vacanti, Nigel Wang.
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United States Patent |
10,186,787 |
Wang , et al. |
January 22, 2019 |
Slot radar antenna with gas-filled waveguide and PCB radiating
slots
Abstract
A slot antenna with the low-cost, light weight features of an
SIW antenna combined with the efficiency of a metallic antenna. The
antenna of this disclosure may use printed circuit board
manufacturing (PCB) processes to form the radiating portion to
create slots and waveguide features with accurate dimensions and
accurate positions. Like a metallic antenna, radio frequency (RF)
energy passes through air in the radiating waveguides instead of a
substrate, which means low insertion loss and high efficiency.
Examples of the antenna of this disclosure may include a metallic
coupling waveguide to carry the RF energy from the RF generating
components of the radar system to the radiated branch waveguides.
The metallic coupling waveguide may be configured to provide
structural support to the PCB radiating portion as well as
backwards compatibility to retrofit existing radar systems with the
antenna assembly of this disclosure.
Inventors: |
Wang; Nigel (Shanghai,
CN), Vacanti; David C. (Renton, WA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Honeywell International Inc. |
Morris Plains |
NJ |
US |
|
|
Assignee: |
Honeywell International Inc.
(Morris Plains, NJ)
|
Family
ID: |
63442556 |
Appl.
No.: |
15/695,910 |
Filed: |
September 5, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01Q
13/10 (20130101); H01Q 21/005 (20130101); H01Q
21/064 (20130101); H01Q 1/38 (20130101); H01Q
13/20 (20130101); H01Q 1/28 (20130101) |
Current International
Class: |
H01Q
1/38 (20060101); H01Q 21/00 (20060101); H01Q
13/10 (20060101); H01Q 21/06 (20060101) |
Field of
Search: |
;343/770 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Le Sage, "3D Printed Waveguide Slot Array Antennas," IEEE Access,
vol. 4, Apr. 2016, pp. 1258-1265. cited by applicant .
U.S. Appl. No. 15/253,494, by Nigel Wang et al., filed Aug. 31,
2016. cited by applicant.
|
Primary Examiner: Baltzell; Andrea Lindgren
Attorney, Agent or Firm: Shumaker & Sieffert, P.A.
Claims
The invention claimed is:
1. An antenna device, the device comprising: a radiating slot plane
comprising: a radiating slot array comprising a plurality of slots;
a printed circuit board (PCB) comprising a first plated layer, a
second plated layer, and a substrate layer, wherein each slot of
the radiating slot array includes an interior surface, wherein: the
interior surface of each slot extends from the first plated layer
to the second plated layer through the substrate layer, the
interior surface of each slot comprises a conductive plated
material, wherein the conductive plated material electrically
connects the first plated layer to the second plated layer; a
radiating waveguide comprising: a radio frequency (RF) conducting
path, wherein the RF conducting path of the radiating waveguide
comprises a gas; a third plated layer; and the second plated layer,
wherein: the second plated layer and the third plated layer
comprise a conductive material, the second plated layer is
electrically connected to the third plated layer and is
electrically connected to the first plated layer of the radiating
plane; the third plated layer is electrically connected to the
first plated layer of the radiating plane.
2. The device of claim 1, wherein the substrate layer of the
radiating plane comprises a first substrate layer, the device
further comprising: a coupling slot plane comprising: a PCB
including the third plated layer, a fourth plated layer, and a
second substrate layer; a plurality of coupling slots, wherein each
coupling slot includes an interior surface, wherein: the interior
surface of the coupling slot extends from the third plated layer to
the fourth plated layer through the second substrate layer, the
interior surface comprises a conductive plated material, wherein
the conductive plated material electrically connects the third
plated layer to the fourth plated layer.
3. The device of claim 2, further comprising a feed waveguide,
wherein: the feed waveguide is configured to conduct RF energy to
the plurality of coupling slots, and the feed waveguide is
configured to provide structural support to the device.
4. The device of claim 1, wherein the radiating waveguide further
comprises a first wall and a second wall, wherein the first wall
and the second wall comprise a plurality of through-holes, wherein
the through-holes include an interior surface, wherein: the
interior surface of each through-hole extends from the first plated
layer to the fourth plated layer through the first substrate layer
and the second substrate layer, the interior surface is plated with
a conductive material, and wherein the conductive material
electrically connects the first plated layer to the fourth plated
layer.
5. The device of claim 1, wherein the radiating waveguide further
comprises a first wall and a second wall, wherein the first wall
and the second wall comprise a plated surface, wherein the plated
surface of the first wall and the plated surface of the second wall
electrically connect the second plated layer to the third plated
layer.
6. The device of claim 1, wherein the gas is air.
7. A method of forming a slot waveguide antenna, the method
comprising: etching a first slot into a first plated layer of a
radiating slot plane, wherein the radiating slot plane comprises a
first printed circuit board (PCB); etching a second slot in a
second plated layer of the radiating slot plane, wherein the second
plated layer is on the opposite side of the radiating slot plane
from the first plated layer; milling a substrate material of a
first substrate layer of the radiating slot plane to form a first
opening between the first slot and the second slot, wherein: a size
and shape of the first opening is defined by an interior surface of
the first opening, and the size and shape of the first opening is
approximately a same size and shape as the first slot and the
second slot; plating the interior surface of the first opening,
wherein the plating of the interior surface of the opening forms an
electrical connection between the first plated layer and the second
plated layer, wherein the first slot, the second slot and the
interior surface of the opening form a radiating slot; etching a
third slot into a third plated layer; etching a fourth slot into a
fourth plated layer, wherein: the third plated layer is on the
opposite side of a coupling slot plane from the fourth plated
layer, and wherein the coupling slot plane comprises a second
printed circuit board (PCB); milling a substrate material of a
second substrate layer of the coupling slot plane to form a second
opening between the third slot and the fourth slot, wherein: a size
and shape of the second opening is defined by an interior surface
of the second opening, and the size and shape of the second opening
is approximately a same size and shape as the third slot and the
fourth slot; plating the interior surface of the second opening,
wherein the plating of the interior surface of the second opening
forms an electrical connection between the third plated layer and
the fourth plated layer, wherein the third slot, the fourth slot
and the interior surface of the second opening form a coupling slot
in the coupling slot plane.
8. The method of claim 7, further comprising: bonding the second
plated layer of the radiating slot plane to a first wall and to a
second wall; bonding the third layer of the coupling slot plane to
the first wall and the second wall, wherein: the first wall, the
second wall, the second plated layer and the third plated layer
form a radiating waveguide comprising a radio frequency (RF)
conducting path, and the RF conducting path comprises a gas.
9. The method of claim 8, wherein the first wall and the second
wall comprise a plurality of through-holes, wherein the
through-holes include an interior surface, wherein: the interior
surface of each through-hole extends from the first plated layer to
the fourth plated layer through the first substrate layer of the
radiating slot plane and the second substrate layer of the coupling
slot plane, the interior surface is plated with a conductive
material, and wherein the conductive material electrically connects
the first plated layer to the fourth plated layer.
10. The method of claim 8, wherein the first wall and the second
wall, comprise a plated surface, wherein the plated surface of the
first wall and the plated surface of the second wall electrically
connect the second plated layer to the third plated layer.
11. The method of claim 7, wherein the radiating slot in the
radiating slot plane is a first radiating slot of a plurality of
radiating slots, wherein: the plurality of radiating slots is
arranged in a plurality of radiating slot rows, each respective
radiating slot row of the plurality of radiating slot rows
comprises a plurality of radiating slots.
12. The method of claim 7, wherein the coupling slot is a first
coupling slot of a plurality of coupling slots and wherein the
plurality of coupling slots is configured to: conduct transmitted
RF energy between a feed waveguide the radiating slot plane; and
conduct received RF energy collected by the radiating slot plane to
the feed waveguide.
13. The method of claim 12, wherein the feed waveguide provides
structural support to the radiating slot plane.
Description
TECHNICAL FIELD
The disclosure relates to slot radar antennae and radio frequency
waveguides.
BACKGROUND
A slot waveguide antenna is a type of antenna used for radar for
high efficiency and high-power handling capability. To reach such
high efficiency, a slot waveguide antenna array may be made of a
metallic material, such as aluminum. A slot waveguide antenna is
typically sensitive to assembly tolerances, meaning that small
inaccuracies or gaps may negatively affect performance. A metallic
waveguide slot antenna may require a costly manufacturing process
to accurately machine the dimensions of the antenna and waveguide.
A slot antenna called a substrate integrated waveguide (SIW) may be
constructed of printed circuit board (PCB) material. SIW creates a
waveguide within the substrate of the PCB. SIW antennae may suffer
higher insertion loss than aluminum antennae, which may limit
applications that could take advantage of SIW.
SUMMARY
In general, the disclosure is directed to an antenna that takes
advantage of the low-cost, light weight features of an SIW antenna
combined with the high efficiency of a metallic antenna. The
antenna of this disclosure may use an SIW process for the radiating
portion to create slots, and other waveguide features, with
accurate dimensions and accurate positions on the antenna assembly.
Like a metallic antenna, radio frequency (RF) energy passes through
a gas, such as air, instead of a substrate, which means less
insertion loss and high efficiency. The antenna of this disclosure
may include a metallic coupling waveguide to carry the RF energy
from the RF generating components of the radar system to the
radiated branch waveguides of the antenna. The metallic coupling
waveguide is accurately positioned and attached with RF techniques
to reduce leakage, mismatch and insertion loss. The metallic
coupling waveguide may be configured to provide backwards
compatibility to retrofit existing radar systems with the antenna
assembly of this disclosure.
In one example, the disclosure is directed to antenna device, the
device comprising: a radiating slot plane comprising: a radiating
slot array comprising a plurality of slots; a printed circuit board
(PCB) comprising a first plated layer, a second plated layer, and a
substrate layer, wherein each slot of the radiating slot array
includes an interior surface. The interior surface of each slot
extends from the first plated layer to the second plated layer
through the substrate layer. The interior surface of each slot also
comprises a conductive plated material, wherein the conductive
plated material electrically connects the first plated layer to the
second plated layer. The antenna device also includes a radiating
waveguide comprising: a radio frequency (RF) conducting path,
wherein the RF conducting path of the radiating waveguide comprises
a gas; a third plated layer; and the second plated layer. The
second plated layer and the third plated layer comprise a
conductive material. The second plated layer is electrically
connected to the third plated layer and is electrically connected
to the first plated layer of the radiating plane and the third
plated layer is electrically connected to the first plated layer of
the radiating plane.
A method of forming a slot waveguide antenna, the method
comprising: etching a first slot into a first plated layer of a
radiating slot plane, wherein the radiating slot plane comprises a
first printed circuit board (PCB). Etching a second slot in a
second plated layer of the radiating slot plane, wherein the second
plated layer is on the opposite side of the radiating slot plane
from the first plated layer. Milling a substrate material of the
radiating slot plane to form a first opening between the first slot
and the second slot, wherein: a size and shape of the first opening
is defined by an interior surface of the first opening, the size
and shape of the first opening is approximately a same size and
shape as the first slot and the second slot. Plating the interior
surface of the first opening, wherein the plating of the interior
surface of the opening forms an electrical connection between the
first plated layer and the second plated layer, wherein the first
slot, the second slot and the interior surface of the opening form
a radiating slot, etching a third slot into a third plated layer,
etching a fourth slot into a fourth plated layer, wherein: the
third plated layer is on the opposite side of a coupling slot plane
from the fourth plated layer and wherein the coupling slot plane
comprises a second printed circuit board (PCB). Milling a substrate
material of the coupling slot plane to form a second opening
between the third slot and the fourth slot, wherein: a size and
shape of the second opening is defined by an interior surface of
the second opening, and the size and shape of the second opening is
approximately a same size and shape as the third slot and the
fourth slot. Plating the interior surface of the second opening,
wherein the plating of the interior surface of the second opening
forms an electrical connection between the third plated layer and
the fourth plated layer, wherein the third slot, the fourth slot
and the interior surface of the second opening form a coupling slot
in the coupling slot plane.
The details of one or more examples of the disclosure are set forth
in the accompanying drawings and the description below. Other
features, objects, and advantages of the disclosure will be
apparent from the description and drawings, and from the
claims.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a diagram illustrating a portion of a slot antenna in
accordance with one or more techniques of this disclosure.
FIG. 2 is a diagram illustrating a side view of a portion of a slot
antenna in accordance with one or more techniques of this
disclosure.
FIG. 3 is a diagram illustrating a top view of the radiating slot
plane of a slot antenna in accordance with one or more techniques
of this disclosure.
FIG. 4 is a diagram illustrating a top view of the coupling slot
layer of a slot antenna in accordance with one or more techniques
of this disclosure.
FIG. 5 is a diagram illustrating etching a slot shape for the top
and bottom conductive layer.
FIG. 6 is a diagram depicting an example milled out slot shape with
the substrate material removed.
FIG. 7 depicts an example milled out slot shape with the interior
surface plated with a conductive material.
FIG. 8 depicts an example radiating waveguide portion before
forming the radiating waveguides.
FIG. 9 depicts an example radiating waveguide portion with the
radiating waveguides partially formed.
FIG. 10 depicts an example radiating waveguide portion with the
radiating waveguides partially formed and coupling slots
visible.
FIG. 11 depicts an isometric view of a plurality of radiating
waveguides of a radar antenna according to one or more techniques
of this disclosure.
FIG. 12 is a diagram illustrating a portion of a radar antenna
including a radiating waveguide termination, in accordance with one
or more techniques of this disclosure.
FIG. 13 is a diagram illustrating a cut-away view of an example
portion of a radar antenna including a radiated portion and a feed
portion.
FIG. 14A is a diagram illustrating an isometric view of a coupling
slot plane of the radiating portion of a radar antenna according to
one or more techniques of this disclosure.
FIG. 14B is a diagram illustrating an assembly view of an example
portion of a radar antenna including a radiated portion and a feed
portion.
FIG. 15 is a flow chart illustrating an example process of forming
a slot antenna in accordance with one or more techniques of this
disclosure.
DETAILED DESCRIPTION
The disclosure is directed to a slot antenna that takes advantage
of the low-cost, light weight features of a substrate integrated
waveguide (SIW) antenna combined with the high efficiency of a
metallic antenna. In some examples, the slot antenna may be used as
a slot radar antenna. The slot antenna of this disclosure may
include a radiated portion and a feed portion. The radiated portion
may include a radiating slot plane, radiating waveguides and a feed
plane, which may also be called a coupling slot plane. The radiated
portion of the slot antenna may use a printed circuit board (PCB)
or similar process to create slots and other waveguide features,
with accurate dimensions and accurate positions on the antenna
assembly. Like a metallic slot antenna, in the slot antenna of this
disclosure, radio frequency (RF) energy passes through air, or some
other gas, instead of a substrate, which means less insertion loss
and high efficiency when compared to a substrate integrated
waveguide (SIW) radar antenna. The feed portion of the slot antenna
of this disclosure may include a metallic coupling waveguide, which
may be referred to as a pedestal or a feed waveguide, to carry the
RF energy from the RF generating components of the radar system to
each branch of the radiating waveguides of the antenna. The
metallic coupling waveguide may be accurately positioned and
attached with RF techniques to reduce leakage, mismatch and
insertion loss. The metallic coupling waveguide may be configured
to provide structural strength and rigidity as well as backwards
compatibility to retrofit existing radar systems with the antenna
assembly of this disclosure.
The slot antenna of this disclosure may include a line of coupling
slots in the center layer of the antenna between radiating
waveguides and feed waveguide to drive the various radiated
branches of the radiating waveguides. The coupling slots are
configured to conduct transmitted RF energy between the feed
waveguide to the plurality of radiating waveguides and further to
the radiating slots of the radiating slot plane to form the radar
transmit beam. The coupling slots are further configured to conduct
the received radar signal to the feed waveguide. The received radar
signal may come from the reflected version of the radar transmit
beam collected by the radiating slot plane after reflecting off a
target. Targets may include aircraft, vehicles, clouds or other
weather features, and similar objects.
FIG. 1 is a diagram illustrating a portion of a slot antenna in
accordance with one or more techniques of this disclosure. FIG. 1
illustrates a sample radiating waveguide comprising electrically
conductive surfaces forming an RF conducting path 24 where the RF
energy travels through air, or some other gas. Though the slot
antenna of this disclosure may be used for other applications, this
disclosure will focus on a radar antenna to simplify the
description. In some examples a slot antenna, according to the
techniques of this disclosure may be used in a mechanical scanning,
pulse modulation application, such as a mechanically steered
weather radar antenna, such as may be used on an aircraft. In other
examples, the slot antenna of this disclosure may be used as a
traveling wave antenna that may be steered electronically.
Radar antenna 10 includes a radiating slot plane 12, radiating
waveguide layer with walls 26A and 26B and conducting path 24, and
coupling slot plane 32. Coupling slot plane 32 may also be referred
to as a feed plane in this disclosure. Radar antenna 10 is
configured to form a radar transmit beam and transmit RF energy
from the radiating slots in the radiating layer. Radar antenna 10
also captures the received radar signal that impinges on the
radiating slot plane from the reflected radar transmit beam.
Radiating slot plane 12 includes radiating slots (14A-14B) in a
radiating slot array on a printed circuit board (PCB), which
includes an outer or first plated layer 16, an inner or second
plated layer 18 and a substrate layer 20. Each radiating slot, such
as 14A and 14B, (collectively radiating slots 14), includes a
plated interior surface 22. The plated interior surface 22 of the
radiating slots in the radiating slot array extends from the outer
plated layer 16 to the inner plated layer 18 through the substrate
layer 20. The plated interior surface 22 of each slot 14A-14B of
the radiating slot array is conductive and electrically connects
the outer plated layer 16 to the inner plated layer 18.
Substrate layer 20 may include materials used in PCB manufacturing,
such as any of the various types of FR4, polyimide-based
substrates, epoxy-based or similar substrates. Fiberglass based
substrates, such as FR4, may have advantages over other types of
substrates in a radar antenna application because of strength,
light weight, ability to withstand shock, and wide temperature
operating range. In addition, a substrate such as FR4 may have the
advantage of significantly lower cost when compared to substrates
such as may be used in an SIW application. To efficiently conduct
RF energy, substrates in SIW applications may be more expensive,
however a slot antenna of this disclosure, which conducts RF energy
through a gas, may not need the higher cost substrates.
Each radiating waveguide in the radiating waveguide layer includes
an RF energy conducting path 24, which is enclosed by a first wall
26A and a second wall 26B. In some examples, the walls, 26A and 26B
may include a substrate material, similar to that in substrate
layer 20, which may be plated with a conductive material. Walls 26A
and 26B may also include through-holes 34. In some examples, walls
26A and 26B may not be plated with a conductive material. Instead,
the interior surface of through-holes 34 may be plated with a
conductive material and act as a wall, similar to an SIW wall.
Further details on walls 26 and through-holes 34 will be described
below in relation to FIG. 2. The conductive plating material of
walls 26, through-holes 34 and plated interior surface 22 may be
the same material as plated layers 16, 18 and 28. Some examples may
include aluminum, copper, or some other conductive alloy or
material that may be used in PCB fabrication.
The RF energy conducting path 24 is filled with some type of gas,
such as air. When compared to an SIW radar antenna, a radar antenna
with the conducting path 24 filled with a gas may have a lower
insertion loss than an SIW radar antenna.
The coupling slot plane 32 includes an inner plated layer 28, which
may be described as the third plated layer 28, in this disclosure.
Inner plated layer 28 forms the fourth side, or plated layer, of
conducting path 24. In other words, conducting path 24 is filled
with a gas and includes four conductive surfaces: the second, or
inner plated layer 18 of the radiating slot plane 12, the third or
inner plated layer 28 of the coupling slot plane 32 and walls 26A
and 26B. The first wall 26A, the second wall 26B, the second plated
layer 18 and the third plated layer 28 are made from an
electrically conductive material and are electrically connected to
each other and electrically connected to the first plated layer 16
of the radiating slot plane 12.
The slot antenna of this disclosure may have advantages when
compared to other types of slot antennae. Any slot waveguide
antenna array may be sensitive to the assembling tolerance. That
is, a small gap may cause a significant performance problem. Thus,
developing slot waveguide antenna array may include high cost and
be difficult to control the consistency. A metallic slot antenna
may require a costly manufacturing process such as brazing (either
salt dip-brazing or vacuum brazing). For example, a thin plate
metallic slot radar antenna may be pre-treated with a flux and
dipped in a bath of sodium. Sodium bath techniques may be expensive
and an environmental hazard, with few manufacturing companies
willing or able to effectively manage the process. As of the date
of this disclosure the cost of such an antenna may be on the order
of US$4000. Machining or 3D printing a metallic radar antenna to
the tight tolerances required makes manufacturing a metallic
antenna expensive. Other processes, such as 3D printing may be
limited by its low speed, high cost and high surface roughness,
which may impact antenna performance.
The high cost and the weight may prevent/reduce/eliminate the
possibility of using a metallic slot antenna in some applications.
For example, the weight of a metallic radar antenna may prevent
using the metallic radar antenna on an unmanned aerial vehicle
(UAV) or smaller aircraft where weight is important. The higher
cost of a metallic radar antenna may put a system including a
metallic radar antenna out of reach for some privately-owned
aircraft, or other applications where cost is important.
An SIW slot antenna is a form of transmission line that creates a
waveguide within a substrate, such as a PCB. The waveguide in an
SIW radar antenna may consist of two lines of holes as the wall of
rectangular waveguide and the metallic layer on the top and bottom
to form a rectangular enclosure around the substrate. The waveguide
of an SIW radar antenna suffers higher insertion loss than the air
in an aluminum waveguide. The insertion loss may be caused by the
substrate, the gap between holes and the surface roughness between
metallic layer and the substrate. An SIW antenna array brings
advantages such as high integration, a thin profile and light
weight. However, for those applications that require very high
efficiency, the SIW technique may be limited.
FIG. 2 is a diagram illustrating a side view of a portion of a slot
antenna in accordance with one or more techniques of this
disclosure. Features with reference numbers in FIG. 2 that are the
same as the reference numbers in FIG. 1, or other FIGS. in this
disclosure, indicate the same feature that performs the same
function. FIG. 2, as with FIG. 1, is one example implementation of
the radar antenna of this disclosure. Other examples may include
features not shown, or exclude features depicted in the figures.
For example, in some implementations, a radar antenna in accordance
with the techniques of this disclosure may not include
through-holes 34. Moreover, FIG. 2 is not shown to scale, as some
dimensions of FIG. 2 have been altered for ease of
understanding.
Radar antenna 10A depicted in FIG. 2 includes four radiating
waveguides 11 in the radiating waveguide layer. The number of
radiating waveguides are for illustration only and other examples
in the figures below will depict additional radiating waveguides.
For clarity, only one of the four radiating waveguides 11 includes
a reference number. As described above in relation to FIG. 1, each
radiating waveguide 11 includes an RF energy conducting path 24
enclosed by an inner plated layer 18, walls 26A and 26B and an
inner plated layer 28. Inner plated layer 18 is the second plated
layer or inner plated layer of radiating slot plane 12 while inner
plated layer 28 is the third plated layer or inner plated layer of
coupling slot plane 32. Conducting path 24 may be filled with a
gas, such as air, argon, or other gas. In some examples, wall 26A
may be substantially parallel to wall 26B. Walls 26A and 26B may be
substantially perpendicular to inner plated layer 18 and inner
plated layer 28. The terms substantially and approximately, as used
in this disclosure mean dimensions or positioning within
manufacturing and measurement tolerances.
The first wall 26A, the second wall 26B, the second plated layer 18
and the third plated layer 28 are made from an electrically
conductive material and are electrically connected to each other
and electrically connected to the first plated layer 16 of the
radiating slot plane 12 as well as the outer plated layer 38 of
coupling slot plane 32.
As described above in relation to FIG. 1, coupling slot plane 32
includes an inner plated layer 28. Coupling slot plane 32 also
includes an outer plated layer 38 and coupling slots 36. Coupling
slots 36 includes a plated interior surface 40 that electrically
connects inner plated layer 28 to outer plated layer 38. In other
words, in some examples all four plated layers depicted in FIG. 2,
that is, outer plated layer 16, inner plated layer 18, inner plated
layer 28 and outer plated layer 38 may all be electrically
connected via radiating slots, coupling slots and/or through-holes
34, described in more detail below. The plated interior surface 40
of coupling slots 36 is similar to plated interior surface 22 of
radiating slots 14, which is also depicted in FIG. 1. For clarity,
only one plated interior surface 22 and plated interior surface 40
has a reference number in FIG. 2. However, each of the radiating
slots 14 and coupling slots 36 includes a plated interior surface
22 and plated interior surface 40, respectively.
In some examples, plated interior surface 40 may be substantially
perpendicular to inner plated layer 28 and outer plated layer 38.
Inner plated layer 28 may be substantially parallel to outer plated
layer 38. Similarly, plated interior surface 22 may be
substantially perpendicular to inner plated layer 18 and outer
plated layer 16. Inner plated layer 18 may be substantially
parallel to outer plated layer 16.
As described above in relation to FIG. 1, each wall, such as 26A or
26B (collectively called walls 26), may include substrate material
with through-holes 34. The surfaces of walls 26, such as the
surfaces indicated by reference numbers 26A and 26B may be plated
with a conductive material, such as copper or similar material. In
some examples, through-holes 34 may not include a plated interior
surface and form no electrical connection. Some examples walls 26
plated with conductive material may have no through-holes 34.
In some examples, through-holes 34 may include a plated interior
surface 35, similar to interiors plated surface 22 and plated
interior surface 40 of radiating slots 14 and coupling slots 36,
respectively. In some examples, through-holes 34 may penetrate the
substrate 30 and inner plated layer 28 of coupling slot plane 32.
Through-holes 34 may also penetrate the inner plated layer 18 and
substrate 20 of radiating slot plane 12. However, in some examples,
through-holes 34 do not penetrate outer plated layer 16 of
radiating slot plane 12, nor the outer plated layer 38 of coupling
slot plane 32. Through-holes 34 may electrically connect outer
plated layer 16 to outer plated layer 38. In some examples,
through-holes 34, with plated interior surfaces 35, may also
electrically connect inner plated layers 18 and 28 to outer plated
layers 16 and 38.
Through-holes 34 with a plated interior surface that electrically
connect outer plated layers 16 and 38 may be configured to act as
the walls of radiating waveguides 11, similar to SIW techniques.
The diameter and spacing of through-holes 34 may depend on the
operating frequency and other parameters of the radar antenna. The
conducting path 24 of the radiating waveguides 11 may include a gas
rather than a substrate, such as the substrate found in SIW
techniques. In examples of a radar antenna according to this
disclosure that use conductive through-holes 34 as walls, the
surfaces of walls 26 may not be plated with a conductive material.
In other words, a conducting path 24 of a radar antenna according
to this disclosure may include several configurations. A first
configuration may include walls 26 plated with a conductive
material. A second configuration may include walls 26 with no
conductive plating and through-holes 34 that have the interior
surface of the through-holes plated with a conductive material that
acts as the walls of conducting path 24, similar to SIW
techniques.
In this second configuration, it may be desirable to configure the
distance between the surface of the unplated wall 26 and the inner
plated surface of through hole 34 to be a small distance. In some
examples, the distance between the surface of the unplated wall 26
and the inner plated surface of through hole 34 may be less than
0.5 mm, which may reduce insertion loss caused by exposed substrate
material in the conducting path 24. Other configurations may
include some combination of through-holes 34 and plated or unplated
walls 26.
In some examples, the substrate of the radiating slot plane and
coupling slot layer may be a copper clad plate or copper clad layer
(CCL) in which copper, or another conductive material, covers both
sides of a 2-layer CCL. The location of the radiating slots,
coupling slots and other features may be placed on the CCL with
high accuracy that may be part of a PCB manufacturing process, for
example by etching, or some similar process. As described above,
accurate feature placement in a slot radar antenna may have
advantages of improved performance, such as efficient RF energy
conduction, accurate beam forming, reduced sidelobes and other
performance factors.
A slot radar antenna according to the techniques of this disclosure
may have advantages over metallic slot radar antennae. As one
example, a slot radar antenna of this disclosure may potentially be
built at a lower cost and be lighter in weight than a metallic slot
radar antenna. An RF energy conducting path filled with a gas, such
as conducting path 24 may have advantages over an SIW because an RF
energy conducting path filled with a gas may have lower insertion
loss when compared to SIW.
A radar antenna of this disclosure may also perform under extremes
of operating conditions while maintaining high performance
standards. For example, a radar antenna for a weather radar
attached to an aircraft may be subjected to extremes in
temperature, such as on the ground in an airport on a hot day
compared to sub-zero temperatures at 30,000 feet. Some examples of
the radar antenna of this disclosure were tested from -75.degree.
C. to +100.degree. C. as well as subjected to condensing water and
freezing cycles, with damage to the antenna nor impact to the RF
performance.
FIG. 3 is a diagram illustrating a top view of the radiating slot
plane of a slot antenna in accordance with one or more techniques
of this disclosure. The radiating slot plane 12 of FIG. 3 is one
example shape and configuration of a radar antenna of this
disclosure. Other examples may include other shapes and
configurations.
Radiating slot plane 12 includes outer plated layer 16 and a
plurality of radiating slots 14 in a plurality of slot rows 42. For
clarity, only a few of the slot rows 42 have a reference number.
Each of the slot rows 42 may correspond to and align with a
radiating waveguide, such as radiating waveguide 11 depicted in
FIG. 2. The length and width of each slot 14 may depend on the
operating frequency range of a radar system or radar device
connected to the radar antenna. The final radiating slots 14 at
each end of a slot row 42 may be placed at a specific distance from
the termination end of the radiating waveguide. The specific
distance may depend on the operating frequency, antenna material,
number of radiating slots 14 in a respective slot row 42, type of
end structure at the end of each slot row 42, such as plated
termination or plated through hole termination, and other factors.
In some examples, the operating frequency may be in the millimeter
wave range or in the microwave range.
The radiating slots 14 may be offset from each other along a slot
row 42. The degree of offset may depend on the position of slot in
the slot row, such as closer to the middle of a slot row 42 or
closer to the end of a slot row 42, as well as the number of
radiating slots 14 in a respective slot row 42. The position of a
radiating slot 14 may be related to energy distribution and beam
forming performance. Adjusting the relative position of a radiating
slot with respect to the walls of the radiating waveguide 11 (not
shown in FIG. 3) as well as relative to other radiating slots may
be selected to control the shape and performance of the radar
transmit beam, such as to reduce sidelobes.
FIG. 4 is a diagram illustrating a top view of the coupling slot
layer of a slot antenna in accordance with one or more techniques
of this disclosure. Coupling slot plane 32, which includes outer
plated layer 38 and coupling slots 36, includes the same functions
and characteristics as described above in relation to FIGS. 1 and
2.
FIG. 4 depicts a row of coupling slots 36 in the center of outer
plated layer 38. In the example of FIG. 4, each coupling slot
corresponds to a respective radiating waveguide 11, as depicted in
FIG. 2, and with a respective slot row 42 as depicted in FIG. 3. A
respective coupling slot is configured to conduct transmitted RF
energy between the feed waveguide to air in the conducting path 24
of a respective radiating waveguide 11. In other words, the
respective coupling slot is configured to couple the feed waveguide
RF energy path to the radiating waveguide RF energy path,
conducting path 24. Conducting path 24 (not shown in FIG. 4)
further conducts transmitted RF energy to the radiating slots 14 of
the radiating slot plane 12 to form the radar transmit beam.
Coupling slots 36 are further configured to conduct a received
radar signal to the feed waveguide from the reflected version of
the radar transmit beam as collected by radiating slot plane 12.
The feed waveguide (not shown in FIG. 4) will be described in more
detail below.
The example of FIG. 4 depicts coupling slots 36 and various angles
to each other. Adjusting the angle of a respective coupling slot
may impact the amount of energy the coupling slot conducts from the
feed waveguide to the radiating waveguide 11. Adjusting the angle
of the coupling slot 36 may adjust the distribution of RF energy
through the radar antenna. Adjusting the distribution of energy may
impact the shape and formation of the RF transmit beam, for example
to reduce energy lost to sidelobes. The length and width of the
coupling slots 36 may depend on the operating frequency range of
the radar antenna, as described above for the radiating slots
14.
FIG. 5 is a diagram illustrating etching a slot shape for the top
and bottom conductive layer. FIGS. 5-7 depict an example process
for creating radiating slots 14 or coupling slots 36. The example
of FIGS. 5-7 will focus on radiating slots as an example, but a
similar process may be used for coupling slots.
FIG. 5 depicts etching a single radiating slot 14C in radiating
slot plane 12. Radiating slot plane 12, as described above in
relation to FIGS. 1-3, includes outer plated layer 16, inner plated
layer 18 and substrate 20. In some examples, radiating slot plane
12 may start as a copper clad PCB multi-layer assembly, which means
outer plated layer 16 and inner plated layer 18 may comprise copper
plating over a PCB substrate, such as FR4 or similar substrate.
Other conductive materials may also be suitable for outer plated
layer 16 and inner plated layer 18.
The example of FIG. 5 depicts using PCB manufacturing techniques to
etch the location and dimensions of radiating slot 14C into the
surface of outer plated layer 16 and inner plated layer 18. The
etching process may expose substrate material 20A in the etched
region of slot 14C. For clarity, only the etched side of outer
plated layer 16 is shown in FIG. 5.
FIG. 6 is a diagram depicting an example milled out slot shape with
the substrate material removed. In some examples, a laser milling
process may be used to remove substrate material 20A from radiating
slot 14D. Some examples of laser milling may only remove the
substrate material and not affect the conductive material, such as
a copper clad material. Therefore, laser milling may have
advantages in retaining the accuracy, consistency and repeatability
of the PCB etching process for the slot location and dimensions, as
well as forming smooth edges. Radiating slot plane 12, depicted in
FIG. 6, includes outer plated layer 16, inner plated layer 18 and
substrate 20 and substrate 20A surrounding the interior surface of
radiating slot 14D.
FIG. 7 depicts an example milled out slot shape with the interior
surface plated with a conductive material. Plating the interior
surface 22 of slot 14 with a conductive material provides an
electrical connection between outer plated layer 16 and inner
plated layer 18.
As described above, the performance of a slot antenna may be
impacted by the accurate location of the radiating slots 14 and
coupling slots 36 as well as accurate the dimension of slot shape.
In some examples, using computer numerical control (CNC) techniques
to make these slots directly in a PCB, the accuracy is may not
result in the desired performance for a slot waveguide antenna
array. Therefore, the weight advantages of the CCL PCB may be
overshadowed by less efficient performance. The PCB etching
combined with laser, or other accurate milling techniques, as
described in this disclosure, may have advantages over other
techniques.
FIGS. 8-10 depict an example of processing steps that may be used
to make the radiating waveguides of the radiated portion of a radar
antenna, according to one or more techniques of this disclosure.
FIG. 8 depicts an example radiating waveguide portion before
forming the radiating waveguides.
FIG. 9 depicts an example radiating waveguide portion with the
radiating waveguides partially formed. Comparing FIGS. 8 and 9
shows the substrate material between walls 26 may be removed, for
example, by a PCB manufacturing process. Some examples of processes
to remove the substrate material to form walls 26 may include
mechanical milling, or some similar process. In some examples, the
substrate material to form the walls may be bonded to either the
radiating slot plane 12 or the coupling slot plane 32. Following
bonding, a process may remove substrate material in the radiating
waveguide portion to form walls 26. In other examples, walls 26 may
be created by another process and bonded to either the either the
radiating slot plane 12 or the coupling slot plane 32. The example
of FIG. 9 depicts the radiating waveguide portion bonded to
coupling slot plane 32.
As described above in relation to FIG. 2, in some examples, the
surfaces of walls 26 may be plated with a conductive material that
is electrically connected to inner plated layer 28 of coupling slot
plane 32. In other examples, through-holes 34 (not shown in FIG. 9)
may be drilled or otherwise formed in walls 26. The interior
surface of through-holes 34 may be plated to form the walls of
conducting path 24. In some examples with plated through-holes 34,
the surfaces of walls 26 may not be plated.
FIG. 10 depicts an example radiating waveguide portion with the
radiating waveguides partially formed and coupling slots visible.
In some examples coupling slots 36 may be formed after forming
walls 26, for example by etching and milling as described above in
relation to FIGS. 5-7. In other examples, walls 26 may be bonded to
coupling slot plane 32 after forming coupling slots 36.
FIG. 11 depicts an isometric view of a plurality of radiating
waveguides of a radar antenna according to one or more techniques
of this disclosure. FIG. 11 illustrates radiating slot plane 12,
radiating waveguide layer with walls 26 and conducting path 24 and
a coupling slot plane 32, which correspond to similar features
describe above in relation to FIGS. 1-10. The view of FIG. 11
illustrates a portion of the example perimeter shape as depicted in
FIGS. 3 and 4 as well as how the radiating waveguides may
correspond to slot rows 42 as depicted in FIG. 3.
The example of FIG. 11 depicts through-holes 34, which may include
plated interior surfaces to act as walls of conducting paths 24 of
the radiating waveguides. As described above, in other examples,
the surfaces of walls 26 may be plated with copper or other
conductive material to contain and direct the RF energy that may
pass through conducting path 24. As described above, the diameter
and spacing of through-holes 34 are features of the radar antenna
of this disclosure that may depend on the operating frequency and
other parameters of the radar antenna.
The example of FIG. 11 depicts an example size, spacing and
location of radiating slots 14, including the offset in relation to
walls 26 and to the other radiating slots as described above in
relation to FIG. 3. As described above, accurate feature placement
in a slot radar antenna may have advantages of improved
performance, such as efficient RF energy conduction, accurate beam
forming, reduced sidelobes and other performance factors. A slot
radar antenna according to the techniques of this disclosure may
take advantage of the accuracy of PCB manufacturing techniques as
well as the advantages of low insertion loss from a conducting path
filled with a gas, such as conducting path 24.
Though not shown in FIG. 11, some examples of the radar antenna of
this disclosure may include additional PCB layers that may include
radar circuitry, such as radar transmit electronics, radar receiver
electronics, processing circuitry, up and down conversion
circuitry, analog and digital circuitry and similar radar
electronics.
FIG. 12 is a diagram illustrating a portion of a radar antenna
including a radiating waveguide termination, in accordance with one
or more techniques of this disclosure. FIG. 12 includes reference
numbers to features also found in other figures in this disclosure,
such as radiating slot plane 12 with outer or first plated layer 16
inner or second plated layer 18 and a substrate layer 20,
through-holes 34, coupling slot plane 32 with outer plated later
38, and conducting path 24.
Termination edge 46 may be a conductive material that may be
electrically connected to, for example, outer plated layer 16,
inner plated layer 18 and the conductive interior surface of
through-holes 34. Termination edge 46 may contain and direct the RF
energy in conducting path 24 of the radiating waveguide.
Termination edge 46 may be formed on the end of each respective
radiating waveguide after other features of the radar antenna are
formed. For example, termination edge 46 may be formed after
bonding radiating slot plane 12, walls 26 and coupling slot plane
32 together.
In some examples, termination edge 46 may completely enclose
conducting path 24. In other examples, as depicted in FIG. 12,
termination edge 46 may only partially enclose the end of
conducting path 24. In other words, conducting path 24 may have an
opening at termination edge 46. The size of the opening may depend
on the operating frequency of the antenna. In some examples, an
opening in conducting path 24 left by a termination edge 46 that
partially covers the end of conducting path 24 may be desirable to
release humidity, condensed moisture or particles, such as dust,
that may enter conducting path 24.
FIG. 12 depicts example radiating slot 14 with plated interior
surface 22 at a distance 48 from termination edge 46. As described
above, accurate feature placement in a slot radar antenna, such as
the location of a final radiating slot 14 of a slot row 42
(depicted in FIG. 3) in relation to the termination edge 46 may
have advantages of improved radar antenna performance. Distance 48
may depend on the operating frequency range of the radar antenna.
The radar antenna of this disclosure may utilize the accuracy of
PCB manufacturing techniques for accurate feature placement at a
reduced cost when compared to machining a metallic radar
antenna.
FIG. 13 is a diagram illustrating a cut-away view of an example
portion of a radar antenna including a radiated portion and a feed
portion. The radiated portion may include a radiating slot plane
12, radiating waveguides 11 and a feed plane, which may be referred
to as a coupling slot plane 32. The feed portion of the radar
antenna of this disclosure may include a metallic coupling
waveguide, which may be referred to as a pedestal, a driving
waveguide or a feed waveguide 50, to carry the RF energy from the
RF generating components of the radar system to each branch of the
radiating waveguides 11 of the antenna.
Feed waveguide 50 may be machined from aluminum, or other similar
material and bonded to the radiating portion at bonding region 52.
Feed waveguide 50, may be bonded to outer plated layer 38 of
coupling slot plane 32 by a variety of methods that may ensure good
connection. RF manufacturing techniques to connect feed waveguide
50 to the radiating portion in an accurate position may be
desirable to reduce RF energy leakage, mismatching and insertion
loss. Some examples of bonding techniques may include soldering,
such as with tin, as well as silver epoxy or other conductive
adhesive. In some examples, the aluminum portions of the antenna
assembly may be plated with nickel to improve the soldering
connection. In some examples, a fixture may be developed to press
the components together to ensure even weight distribution during
assembly. In some examples positioning studs or other protrusions
may be formed in feed waveguide 50 to align with holes, such as via
holes, in the PCB portions of coupling slot plane 32 for accurate
positioning.
The example of FIG. 13 depicts feed waveguide 50 configured to
cover coupling slots 36 to transfer transmitted RF energy to the
plurality of radiating waveguides 11 as well as transfer reflected
received RF energy from the radiating waveguides 11 to receiving
electronics of a radar system. This configuration is also depicted
in FIG. 14B.
As described above, for example in relation to FIGS. 1 and 2, the
additional features of the radiating portion depicted in FIG. 13
include walls 26A and 26B, through-holes 34, inner plated layers 18
and 28, which border conducting path 24. Coupling slot 36 includes
plated interior surface 40, and radiating slot 14 includes plated
interior surface 22, which forms an electrical connection to outer
plated layer 16. Radiating slot plane 12 includes substrate 20 and
coupling slot plane includes substrate 30. As described above,
various materials may be used as a substrate. FR4 is an example of
a low cost substrate material that may be suitable for a radar
antenna with air in the conducting path 24, according to the
techniques of this disclosure. FR4 may have advantages in cost when
compared to an SIW antenna, which may require a more costly high
frequency, low dielectric constant (Dk) and low insertion loss
substrate material.
In some examples, a feed waveguide may be formed by additional PCB
layers rather than a metal feed waveguide such as feed waveguide
50. A metal feed waveguide may have advantages over additional PCB
layers because the stack-up of PCB layer structure may make the PCB
process more complex and costly. Also, the total thickness of the
PCB may be limited depend on the capability of different PCB
manufacturers. The combination of a radiated branch waveguide on
the PCB board and a one-side open metal pedestal to form the feed
waveguide and provide structural support along with RF
manufacturing techniques may offer advantages of lightweight, low
cost, and efficient radar antenna performance when compared to
other techniques. The one-side open metallic coupling waveguide may
have advantages in lower cost and easier to manufacture when
compared to machining a more complex metallic slot waveguide
antenna.
FIG. 14A is a diagram illustrating an isometric view of a coupling
slot plane of the radiating portion of a radar antenna according to
one or more techniques of this disclosure. FIG. 14A depicts
coupling slot plane 32 with coupling slots 36 in outer plated layer
38.
FIG. 14B is a diagram illustrating an assembly view of an example
portion of a radar antenna including a radiated portion and a feed
portion. Feed portion 54 is configured to support radar antenna 10B
as well as conduct RF energy to and from coupling slots 36 (not
shown in FIG. 14B). Radar antenna 10B corresponds to radar antennae
10 and 10A described above in relation to FIGS. 1 and 2.
In the example of FIG. 14, feed portion 54 includes feed waveguide
50, which corresponds to feed waveguide 50 described above in
relation to FIG. 13. Feed portion 54 may also include one or more
support structures 56 and one or more positioning structures
58.
As described above in relation to FIG. 12, feed portion 54 may
include one or more termination edges, such as termination edge 64.
In some examples, termination edge 64 may completely enclose
conducting path of feed waveguide 50. In other examples, as
depicted in FIG. 14B, termination edge 64 may only partially
enclose the end of the conducting path leaving an opening 62. The
size of opening 62 may depend on the operating frequency of the
antenna. In some examples, opening 62 in the conducting path left
by a termination edge 64 that partially covers the end of the
conducting path may be desirable to release humidity, condensed
moisture or particles, such as dust, that may enter the conducting
path of feed waveguide 50.
Support structures 56 may provide structural support to radar
antenna 10B, which may be desirable for applications where radar
antenna 10B may be subject to vibration or shock. For example, in
applications where radar antenna 10B may be part of a radar system
on a vehicle, such as an aircraft. The depiction of support
structures 56 in FIG. 14B are just one example of possible support
structures. Support structures 56, and other features of feed
portion 54 may also be configured for compatibility with existing
radar systems that use a metallic slot waveguide antenna. In other
words, radar antenna 10B may be configured to replace an existing
metallic slot waveguide antenna on an existing radar system with
little or no modifications to the existing radar system.
Positioning structures 58 may be studs, or other features that may
accurately position the feed portion 54 on radar antenna 10B. In
some examples, positioning structures 58 may be configured to mate
with via holes or other features of coupling slot plane 32 of radar
antenna 10B.
FIG. 15 is a flow chart illustrating an example process of forming
a slot antenna in accordance with one or more techniques of this
disclosure. FIG. 15 is just one example process for forming a radar
antenna of this disclosure. In other examples, the steps listed may
be performed in a different order, the process may include
additional steps not listed or exclude some listed steps.
For clarity, the description of forming a slot antenna in relation
to FIG. 15 may focus on forming a single feature, for example, a
single coupling slot in the coupling slot plane. However, as
described above in relation to FIG. 4, the coupling slot plane 32
includes a plurality of coupling slots 36. Similarly, the radiating
slot plane 12, described above in relation to FIG. 3 includes a
plurality of radiating slots 14 arranged in a plurality of slot
rows 42. The steps of FIG. 15 may apply equally to the plurality of
slots, through-holes and other features in a slot antenna of this
disclosure. The steps of FIG. 15 will be described primarily in
relation to the features of FIGS. 2 and 14, unless otherwise
mentioned.
In radiating slot plane 12, etch a first slot 14C into the first or
outer plated layer 16 of a clad PCB, such as a copper clad PCB
(100) as shown in FIG. 5. The dimensions, such as length, width and
shape, of slot 14 may depend on the operating frequency or other
parameters of the radar antenna. Etching the slot 14C into outer
plated layer 16 may leave behind substrate material of the PCB
radiating slot plane 12, as depicted by substrate 20A in FIG.
5.
On the opposites side of radiating slot plane 12 etch a second slot
in the second or inner plated layer 18 of radiating slot plane 12
(102). Etching the second slot into inner plated layer 18 may leave
behind substrate material, similar to that depicted by substrate
20A in FIG. 5. The second slot may be etched at the same time as
first slot 14C, or may be etched in two separate etching steps. The
second slot may be configured to be directly opposite and have the
same dimensions as slot 14C.
As shown in FIG. 6, mill substrate material 20A of the radiating
slot plane 12 to form a first opening 14D through the substrate
layer between the first slot and the second slot (104). As
described above, laser milling may provide advantages over other
techniques in retaining the accurate shape and dimensions of the
PCB etching process in the interior surfaces of the opening between
the first slot and the second slot. The opening, as defined by the
interior surface, may have approximately the same shape and
dimensions as the first slot and the second slot. As described
above, accurate dimensions and placement for radar antennae may be
desirable for radar performance, such as minimizing leakage,
reducing sidelobes, and similar factors.
Form a radiating slot 14 by plating the interior surface of the
first opening. Plating the interior surface 22 of the opening may
form an electrical connection between the first plated layer 16 and
the second plated layer 18 (106). In other words, the combined
etched first slot 14C, the etched second slot and the milled and
plated interior surface 22 of the opening form the radiating slot
14. The etching, milling and plating steps may be repeated for the
plurality of radiating slots 14 in the plurality of slot rows 42.
The plating material of interior surface 22 may be the same or
different material than the material of plated outer plated layer
16 and inner plated layer 18. As one possible example, the material
of outer plated layer 16 and inner plated layer 18 may be copper,
or a copper alloy. The material of interior surface 22 may be the
same copper alloy, or may be a different composition copper alloy,
or some other compatible conductive material.
In a second, clad PCB, etch a third slot in this third PCB layer
(108). The dimensions of the third slot may be the same or
different dimensions as the radiating slot 14. The dimensions of
the third slot may depend on the operating frequency or other
parameters of the radar antenna. As described above, etching the
third slot may leave behind substrate material, which may have
similar structure and appearance to substrate 20A depicted by FIG.
5.
Similar to the second slot described above, etch a fourth slot in
the opposite side of the second, clad PCB (110). The second PCB may
be configured as the coupling slot plane 32. In other words, the
third slot in the third PCB layer corresponds to the inner plated
layer 28 of coupling slot plane 32. The fourth slot in the fourth
PCB layer corresponds to an etched slot in the outer plated layer
38 of coupling slot plane 32.
Similar to the description above in relation to step 104, mill the
substrate material of the coupling slot plane 32 to form a second
opening between the third slot and the fourth slot (112). The
second may appear similar to the first opening defined by the
interior surfaces of the substrate between the etched slots as
depicted in FIG. 6. The size and shape of the second opening may be
approximately the same size and shape as the third slot and the
fourth slot.
Similar to the description above in relation to step 106, form a
coupling slot 36 in coupling slot plane 32 by plating the interior
surface of the second opening (114). The plating of the interior
surface of the second opening may form an electrical connection
between the third plated layer, inner plated layer 28 and the
fourth plated layer, outer plated layer 38. In other words, the
third etched slot, the fourth etched slot and the interior surface
of the second opening may form a coupling slot 36 in the coupling
slot plane 32. As described above, the plating material of the
interior surface of the second opening may be the same or different
than the material for the inner plated layer 28 and outer plated
layer 38. Also, the plating and substrate material of the radiating
slot plane 12 may be the same or different as the plating and
substrate material of the coupling slot plane 32.
Other steps, not shown in FIG. 15, may include bonding the walls 26
to the coupling slot plane 32 and radiating slot plane 12. In some
examples wall material may be bonded to either coupling slot plane
32 or radiating slot plane 12 and removing material to form walls
26. In other examples, walls 26 may be formed and bonded to
coupling slot plane 32 and radiating slot plane 12. Forming the
walls 26 is described in more detail above in relation to FIGS.
8-11.
In some examples, through-holes 34 may be formed in walls 26. The
interior surface 35 of through-holes 34, may be plated and form an
electrical connection to one or more of outer plated layer 16,
inner plated layer 18, inner plated layer 28 and outer plated layer
38. Plated through-holes 34 may act as walls of conducting paths 24
of the branches of radiating waveguides 11, similar to
through-holes as used in SIW techniques. In other examples, the
surfaces of walls 26 may be plated with conductive material and act
as walls of radiating waveguides 11.
In some examples, a metallic coupling waveguide, which may be
referred to as a pedestal, a driving waveguide or a feed waveguide
50 as depicted in FIGS. 13 and 14B, may be bonded to the radiating
portion of the radar antenna. Feed waveguide 50, may be configured
to transfer RF energy from the RF generating components of the
radar system to each branch of the radiating waveguides 11 of the
antenna as well as to transfer the received RF energy received by
the radar antenna to the radar receiving electronics.
Various examples of the disclosure have been described. These and
other examples are within the scope of the following claims.
* * * * *